Swivel pipe joint



Feb. 26, 1952 K. 1. POSTEL SWIVEL PIPE JOINT Filed Dec. 14, 1946 FIG.

FIG.3.

FIG. 2.

INVENTOR. KENNETH I. POST EL BY KT ATTORNEY.

Patented Feb. 26, 1952 SWIVEL PIPE JOINT Kenneth 1. Postel; Detroit, Mich., assig'norto Vicke'rs Incorporated, Detroit, Mich., a corporationof Mi'cliigan' Application December 14, 1946-,SerialNo.-716,312-

' I1'Claims. l.

'Ehis invention relates to power. transmissions, particularly to those ofihe type. comprising, two or..mre fluid. pressure energy translating. devices, one of. which. may function as a pump. andLanother. as a fluid motor.

. Therinvention relates generally to-.variable. displacement hydraulic .motor-pump. devices. of the type employing a. swinging yokesupporting a cylinder. barrel. in. which; multiple pistons of the axially. reciprocable type are employed. More specifically the inventionrelates to rotatable. hydraulic couplings. such. as the.hollow pintleconstruction on which a. motor-pump. yoke pivoted to the housing.

One. of. thedifficulties with the hollow. pintl'e structure is to. maintain a. satisfactory peripheral seal; against the.pintle.. Various flexibleannular sea-ling elements have .zbeen. employed. suchas leather... mounted in .an' annular groove: andheld inasealingr contact with the periphery of...the pintle. Atthehigher; pressures. used in present day practice, aslight. increase in. clearance be.- tween the pintle and housing. might permit .the seal to. blow out andrequire repacking the. joint. In-1 earlier construction,-- when the pintle. was journalled-in theyoke, the" critical sealing areaof the pintles-was around. its. periphery. Under the present inventionthe relative rotation is atthe end: face ofthe pintle, the. pintle being: adapted to rotatein unison-.withthe yoke. The. present sealing. element is in the. form. of an. annular metalbushingadapted tobear. axially. againstthe end face of the. yokepintle or. pressure. fluid conduntor. ..The. sealing- .element. is substantially pressure balanced and adapted; ta moveaxially into. end:v abutment. with. .the. pintle. or. conductor and. maintain a uniform sealing contacttherewith regardless of. pressurevariations.

Therefore, one. of .theobjects of. this. invention is to.- providea. pressure balanced annular. sealing elementadapted. to. move axially into sealing engagement-with. the mating, surfaceon the end face of. the conductor. to besealed.

The. problem of sealing rotating peripheral'surfaceshas. always been a d'iifi'cult one but; when the relative movement is axial, the mating .sur;-- faces. can be. readily sealed with a torus type; of seal; In. the present swing; joint" structure'there are. no rotating peripheralisurfaces: to be sealed si'ncethe major relative movement'is betwee the end faces of the conductor and sealingelement;

Therefore, another object of the invention is to provide ahydraulic rotating coupling in which the rotating element is. sealed on its" abutting end face and is free of relative peripheral rotation requiring pressure seals.

Another-1 object is" to" provide pressure respon- 2. sive means for'urgingthe sealing element-axially into sealing contact with the conductorto be sealed.

.Still another object is to provide resilientmeans for urging. the sealing element into sealing contact. with the conductor independent of :operating, pressure.

The present invention is' particularly-applicahle to the variable displacement motors and pumps of the type employingswinging yokes pivoted on hollow. pintles. By" fastening the yoke to a pair of pintles and journalling the pintles in the frame, an annularsealing element can-be mounted in the frame. in' sealing abutmentwiththe end oithe. pintle.

Therefore.. another .object or thepresent invention isto provide. a noveheconomical pi'ntl'e constructionv for avariabl displacement motorpump, employing the swingingyokedesign.

Further objects and advantages of' the present invention will be apparent from the" following description. reference being had to theaccompanying drawing wherein a-preferredform of the present invention is" clearly shown.

In the drawing:

Figure 1 is. a sectional viewof ahYdrEtuIicnlotor-pump device employing azpreferred form of the invention.

Figure 2 is an enlarged sectional view'ofthe novel pintle" construction shown in Figure 1.

Figure 3' is a diagrammatic illustrationof'the theoretical; pressure balance of l the sealing element; In detail, themotor-pump' device disclosed in Figure 1 includes ashaft l0 connected to a-cylinder' barrel l2 which rides on a valve plate l'l mounted in theyoke l6 which is pivoted to frame I 8 by means of pintles" 20. and. 22.

The shaft I0 is journalled" in bearings M and 26 and. is provided with a flanged. portion" 2-8 which. is connected. by: piston rods 30 to" pistons 32. reciprocably mounted in? cylinders 34;". Cylinders, 34. are connected by ports 36 topassages 38. and 40 which in turn communi'cate witn the central bores 42. and 44" of the hollowipintlesfl and 22- and the external connections 01" frame flanges 4B and 48, respectively.

The. yoke. I6 is fastenedto pintles!!! andZZ'and secured against relative rotationJoy means" of torus seals-50. The pintles 20 and 22 are fournalledinbearings 521. and 54 and free torot'at'e in the frame I8.

Annular. metal. sealing-elements 56 and 58 are mountedin the flangesdfij and. 48,.respectively', of stationary frame. l8, and. are adapted. to move axially into sealing contact withtheendifacesfill and-62. of pintles 20 and 22, respectively; Torus seals 64 are employed on the peripheral surface of the sealing elements 55 and 58. A wave washer or resilient element 55 (Figure 2) is provided to urge the element 55 into sealing contact with pintle 25.

A shaft seal 15 is provided and comprises a guide chamber '12 in which a generally cylindrical sealing element 14 is located and adapted to be moved radially into sealing contact with shaft H). A resilient element or spring 15 is positioned in the guide chamber 12 in back of the sealing element I4 for extruding the element radialy from the chamber 12 into sealing contact with shaft [5. A passage 18 conducts pressure fluid to the chamber 12 in back of the element 14 whereby any increase in pressure will directly aid the spring 15 and provide a greater sealing force in proportion to the increase in pressure.

In Figure 2, it Will be observed that the sealing element 55 is adapted to shift axially whereby its annular face 80 may be moved to a point adjacent face 55 of pintle 20 and maintain sealing contact therewith. The internal edge of the sealing joint formed by the intersection of the mating surfaces 68 and 80 and bore 42 is in direct communication with the continuous passage formed by the pintle 28 and element 55. Since it is impossible to exclude pressure fluid from such a joint or abutment of surfaces, an annular film 82 of pressure fluid is maintained between the adjacent surfaces supplied from the passage or bore 42. The external edge or periphery of annular film 82 is connected to atmosphere or a relatively lower pressure than maintained in bore 42. Any fluid escaping from the film 82 or riphery of the adjacent surfaces 50 and 85 will be conducted through the cage of bearing 52 to the inner case 95 and thence to the drain.

In Figure 3, the relative pressure forces on the sealing element 55 are illustrated diagrammatically. The pressure P represents a unit of pressure in the passage or bore 42 which is exerted at the point of intersection of the annular surfaces 55 and 85 with the bore 42, while the pressure at the periphery of said annular surfaces D and 80 is zero.

The mean effective unit pressure on the entire annular surface 85 is approximate one-half the maximum pressure. Therefore, in order to balance the pressure on the element 55, the annular area 84 was made approximately one-half the area 85. Actually the area of 84 is slightly greater than one-half the area of 85 and consequently the sealing element 55 is actually unbalanced and adapted to be urged toward the mating surface 55 of the pintle 25, in response to pressure. The opposed pressure forces against element 55 are illustrated by the groups of arrows 88 and 90 and theoretically are substantially balanced. The

annular step 92 is located in chamber 94 which in turn is hydraulically connected to the case 95 through the cage of bearing 52 and consequently is subject to tank pressure and does not affect the pressure balance of sealing element 55.

In operation, with the motor-pump device of Figure 1 being operated as a pump, the rotating group would be driven by shaft connected to a prime mover (not shown). Hydraulic fluid would be drawn in through bore 44 of pintle 22 and directed to cylinder 34 through passage 45. After compression in the cylinder barrel l2, the pressure fluid is discharged through passage 38, pintle 25, sealingv element 55 and external connecting flange 45.

The length of stroke and displacement of the pump is varied by swinging the yoke 15 to either side of its center position. The yoke I5 is pivoted to the frame by means of pintles 25 and 22. The pintles are pressed into the torus seals 55 and rotate with the yoke 15 in bearings 52 and 54 of frame l8.

The sealing element 55 is non-rotatively fastened to the frame 18 by torus seals 54 but relatively free to move axially in the bore of external connection and be urged into sealing engagement with the end face 65 of pintle 25, (Figure 2). Therefore, during rotation of the yoke the pintle surface rotates in relation to the sealing element surface 85, and is maintained in sealing contact therewith by means of operating pressure. No matter how tightly the abutting surfaces 65 and 85 are pressed together, internal pressure fluid will enter the minute separation and establish a film 82 extending to the external edge of the mating surfaces.

The pressure drop from the internal to the external edge of the film will normally be equal to the value of the pressure in the bore. In other words, the film pressure drops gradually toward the external limit and the average pressure in the film 52 between the mating surfaces 50 and 80 is one-half the maximum pressure at the internal edge of the film. Therefore, the total force tending to separate the mating surfaces can be calculated by multiplying the area of one of the adjacent mating surfaces by one-half the value of the maximum pressure.

To counter-act the pressure forces of film 82 tending to break the seal by separating the sealing element from the pintie 20, a counterbalancing annular pressure area 84 is provided on sealing element 55 responsive to fluid pressure from the internal bore of the passage. Since area 84 is subject to maximum pressure over its entire surface as compared with an average of one-half that pressure on area 85, it is evident that an exact balance of forces capable of pre venting axial movement of the element 55, would prevail only if area 84 is one-half area 85.

However, it is desirable that element 55 be maintained in sealing contact with pintle 20 regardless of variations in pressure and therefore the area 84 is made slightly larger than half the area of 85. During starting operation of the pump before any pressure has been developed, the resilient element or wave washer is provided which constantly urges the sealing element 55 into sealing contact with pintle 25.

It will thus be seen that the present invention has provided a hydraulic swing joint or pintle construction having excellent sealing characteristics and suitable for high pressure operation without unduly loading or binding the pintle-and iii) yoke. This is accomplished by means of an annular sealing element adapted to shift axially into sealing contact with the end face of the pintle or rotating conductor and maintain a uniform seal regardless of variations in operating pressure fluid.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a rotatable pressure fluid coupling, a retatable conductor, a relatively non-rotatable annular sealing element abutting the end face of the conductor to form a continuous fluid passage,sealing surfaces on the adjacent faces of the conducsegue-ear.

fluidsupplied ffoni the passage and meansonthev.'

element forming two endarea s eppdsite thseal} 'i'ng surface only= dneof'which is lxiio'se'd te pressure from the passage; saidf one' 'area e'in'g pro-9;: portioned to co'unterbalance the ressure-remain pa'ssagei seal ing surf aces" ontlieadjacent races-citric conductor'and,

forming two's'eparate end areas 'o'pposltethe sal ing surface onlyone ofWhich' 'sexpos eel acr s, v

sure within the --pa'ss'age;-'the-' end-area pressure within the passage being propo accent to counterbalance the pressure force ihtlie film tendingto separate the adjacent seal and t matel-y' one-half theproj'cted area of the sealing surface of theelement.

3. In a rotatablepressure fluidcoupling, a ro tata'bl'e conductor; aEre'latively' non-rotatable an -f rfaces" a 'ta-in'said surfaces inmost-ant sealing contact, and having semen-tee area approxia nular sealing element abutting th'e' enctfac-of the conductorl -tovforma continuousT fluid passage, sealing surfaces on the adjacent faces of the conductor and element separatedby a filmo'fpre'sgf sure flui'd supplied:- from tne passa e, and means on the element forming t'w'o opposite-the sealing surface only-one of -whi'clr is exposed to pressure from thr passage said end areal exposed to pressure in the passage being.

proportioned to counterbalance the pressufaforce in thefil'rn' tending to separate are adj arfti sea -l ing surfaces and maintain said surfaces in sub} stantial sealing contact, and resilient means for maintaining the adjacent surfaces in sealing con-' tact independent of fluid pressure.

4. A hydraulic coupling comprising a pair of conductors, one rotatable and the other relatively stationary, an annular sealing element mounted substantially non-rotatably in the stationary conductor but adapted to move axially toward or away from the end face of the rotatable conductor, said conductors and annular sealing ele-- ment forming a continuous hydraulic passage, sealing surfaces on the adjacent end faces of the rotatable conductor and element separated by a thin film of pressure fluid supplied from the passage, and means on the element forming two separate and approximately equal end areas opposite the sealing surface, only one of which is exposed to pressure within the passage, the end area exposed to pressure in the passage being proportioned to exert only a slight resultant force on the element and maintain the adjacent surfaces of the element and conductor in uniform sealing contact regardless of pressure variations in the passage.

5. A hydraulic coupling comprising a pair of conductors, one rotatable and the other relatively stationary, an annular sealing element mounted substantially non-rotatably in the stationary conductor but adapted to move axially toward or away from the end face of the rotatable conductor, said conductors and annular sealing element forming a. continuous hydraulic passage, sealing surfaces on the adjacent end faces of, the rotatable conductor and element separated by a thin film of pressure fluid supplied from the passage,

parate end-- areas- 'ele'ment and conductor in' uniferm seali'ng 6, and-" ivh icl'i is nueommumcatro relatively lower pressure -are 1 pressures-seas oilthe element ommun ication with the' pr'ssur' fiui'd inl the passagysaid"p sure a1easf being 'propor tioned to' exerts r'iet resultant force on the element and uni form -sealingcontactregardless or'pressure variations in the passage} o'ne of the: differenti sur" "area's' -bei-ng the face' of the se i'n adjacent-the rotatablecond'u'ctor'and sri the averagdfliiid pressure=- of the oams-the: other having a projected area 'appro-xim 'ately 'one-half the" i-rrjet-ited" first area 'a'nd directl'y' expos'eds tothe assag'e-pressure.

6L1; hydraulic-couplingcomprising apair= of conductors, one' rotatable' and tl i'e other relatively stati'onary, an annular sealing element-mounticonductor but adapted to i move -2zxially' toW-ard -or away from the end face offthe rotatable -cond-uet'or; said" conductors and annular sealing ele nient forming' a continuous-hydraulic assage; sealing-surraces on-the adjacent ehd fac'esi'of the rotatableconductor and element separated: by a m of'pressur fluidslipp1ied*fi ofir tlie passage; and differential pressures areas on" th elerh ent' u communieation witn thc 'pressur uid iir-the' passage, said-pressureareasbeing-adapted to xert a slight ne't resultant foree om fill element and maintain thead'jacent-surfa'ce regardless of pressure variations I in the p and resilient -means"- formaintaining the d-jacent surfaces in sealing. c'ontact-ihdependene of 'fl" pressure:

t; In arotatable li'ydraulicpressurefluiifcon pnfn a" rotatabreconductor armare-leaves nonrotatable annula'rsealing-element withtheir-"end faces in substantial sealing abutment and forming a continuous hydraulic conductor, said sealing element beingadapted to be moved axially in response to fluid pressure to provide a pressure controlled restricted annular passage between the end faces and adapted to conduct pressure fluid from the internal bore of the conductor to a point external of the passage maintained at relatively lower pressure, and means comprising a pressure effective surface associated with the element responsive to fluid pressures in the conductor adapted to urge the sealing element toward the rotatable conductor, the pressure efiective area of the surface being proportioned to slightly overbalance the pressure force in the film tending to separate the sealing element from the conductor.

8. In a rotatable hydraulic pressure fluid coupling, a rotatable conductor and a relatively nonrotatable annular sealing element with their end faces in substantial sealing abutment and forming a continuous hydraulic conductor, said sealing element being adapted to be moved axially in response to fluid pressure to provide a pressure controlled restricted annular passage between the end faces and adapted to conduct pressure fluid from the internal bore of the conductor to a point external of the passage maintained at relatively lower pressure, and 9, separate pressure surface on the element responsive to fluid pressures in the conductor and havin an effective pressure area adapted to urge the sealing element toward the rotatable conductor and proportioned to slightly overbalance the pressure force in the film tending to separate the sealing element from the conductor, and. resilient means for maintaining the adjacent surfaces in sealing contact independent of fluid pressure.

9. In a hydraulic coupling, stationary androtatable fluid conductors connected by an annular sealing element to form a continuous hydraulic passage, said element being non-rotatively fixed to one conductor but free to move axially therein, an annular sealing surface on the end face of the other conductor adjacent a mating surface on the element, a film of fluid maintained between the adjacent mating surfaces, said film being in communication internally with the pressure fluid in the passage and externally with a relatively lower pressure effective surface, and a pressure area on the opposite end of the element subject to the internal pressure of the passage and the pressure effective area of the surface being proportioned to slightly overbalance the pressure force against the mating surface of the element thereby maintaining the element in axial sealing contact with the conductor.

10. In a hydraulic coupling, stationary and rotatable fluid conductors connected by an annular sealing element to form a continuous hydraulic passage, said element being non-rotatively fixed to one conductor but free to move axially therein, anannular sealing surface on the end face of the other conductor adjacent a mating surface on the element, a film of fluid maintained between the adjacent mating surfaces, said film being in communication internally with the pressure fluid in the passage and externally with a relatively lower pressure area, and means on the element forming two separate end surfaces only one of which is exposed to pressure in the passage, the surface exposed to pressure having a projectedpressure area slightly greater than half the-projected area of the mating surf-ace on the element and proportioned to counterbalance the pressurel wforce against the mating surface of the element thereby maintaining the element in axial sealing contact with the, conductor.

11. In a hydraulic coupling, stationary and rotatable fluid conductors connected by an annular sealing element to form a continuous hydraulic passage, said element being non-rotatively fixed to one conductor but free to move axialb' therein, an annular sealing surface on the end face of the other conductor adjacent a mating surface on the element, a film of fluid maintained between the adjacent mating surfaces, said fllm being in communication internally with the pressure fluid in the passage and externally with a relatively lower pressure area, means on the element forming two separate end surfaces only one of which is subject to the internal pressure of the passage said surface exposed to pressure being proportioned to counterbalance the pressure force against the mating surface of the element thereby maintaining the element in axial sealing contact with the conductor, and resilient means for maintaining the element in sealing contact with the conductor independent of fluid pressure.

-- 1 I. POSTEL...

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS France of 1926 

